Razer Core X + RX 580 + 2019 15" MacBook Pro + LG 38GN950 (3840x1600) >75Hz Issues
I recently bought a Razer Core X to put my RX 580 in to be an eGPU for my 2019 15" MacBook Pro. I connected it via thunderbolt with the included Razer cable to my LG 38GN950 ultra wide which runs at 3840x1600. Out of the box, everything worked, but when I went to display settings to make sure I was getting the full 144Hz that the monitor can do, it was only running at 75Hz. As soon as I upped the refresh rate to 144Hz, my external display goes black. Also, for whatever reason, I cannot run in clamshell mode with any refresh rate - I can mirror and extend display with full resolution, but as soon as I go to clamshell, the screen goes black. This wasn't an issue with my previous monitor, so is it a bandwidth issue? Although that previous monitor was 4k, which is 3840x2160, which is more pixels to drive.
Anyways, I've tried many things, and scoured the internet for a solution, but alas have found none.
I hope someone can help!
Do you have an external keyboard and mouse connected to the MacBook Pro for clamshell mode?
Check the power settings - prevent computer from sleeping automatically when the display is off? Or other option?
Did you try using SwitchResX to create timings with different refresh rates to see what the max refresh rate is before it goes black?
I think 144 Hz should work with 3840x1600 at 8 bpc. If you want RGB or 4:4:4 with HDR or 10 bpc, then 127 Hz is the max (you may need to go lower - like 120 Hz).
@joevt, thank you for all of your help - I have made some progress. After installing SwitchResX, I found there was a setting for HiDPI - when I switched to 3840x1600 144Hz, with HiDPI disabled, I'm now able to get my MacBook to drive the monitor without going black. Awesome!
I'm still having issues with clamshell mode, however. My "Energy Saver" settings under the "Power Adapter" tab are as follows:
Automatic graphics switching: On
Turn display off after: 15Min
Prevent computer from sleeping automatically when the display is off: On
Put hard disks to sleep when possible: Off
Wake for Wi-Fi network Access: Off
Enable Power Nap while plugged into a power adapter: Off
I have both a bluetooth magic keyboard + trackpad, and a USB mouse connected to the MacBook for clamshell mode.
@christopher_ryan_1, I tried 3800x1600 144Hz on my RX 580 eGPU without issue using either lowres or HiDPI (which is actually 7680x3200). The HiDPI mode scales to 3800x1600 144Hz output. I tested in Big Sur but I don't think Catalina should be different. A screenshot of the timing info for the working mode and the non-working mode might be informative.
Did you check https://support.apple.com/en-ca/HT201834 ? It says the AC adapter needs to be connected or a display that provides power over USB-C. I think the Razer Core X provides sufficient power? Well, try the AC adapter that comes with the MacBook Pro anyway.